1. Field of the Invention
The present invention relates generally to an electrode used in a tungsten inert gas (TIG) welding operation, and more particularly, to a cracking apparatus and method for producing an improved cruciform-shaped crack in a tip of the electrode for enhancing electrode life and arc-starting capability.
2. Description of the Prior Art
Various tip configurations of thoriated tungsten electrodes have been used in the past for TIG girth welding of nuclear fuel rods. In recent years, it has been found that a "flat split" end configuration on a welding electrode tip, specifically one having a 0.040 inch diameter, provides many benefits, especially in longer electrode life and more reliable arc starts. The ideal configuration of the split or crack is a cruciform shape, centrally and symmetrically located on the flat end face of the electrode tip. The preferred location of crack origin (the length of the split) is 0.06 inch from the end face. Operating experience has shown that both the symmetry and length of cracks are crucial to successful performance of the electrode in service. One example of a cruciform slot in a welding electrode tip is illustrated in U.S. Pat. No. 4,471,208 to Edmonds.
Heretofore, the ideal crack configuration has not been easily achieved owing to the tooling used to produce it. Prior to the present invention, electrode tips have been configured by hand, by an operator using a pair of ordinary hand cutters or "dykes". The success of this technique is highly dependent on the level of operator skill in terms of dexterity, vision and kinesthetic "feel". Even the most highly skilled operators can not produce crack configurations which are consistent from one electrode tip to the next. There is no way of accurately controlling crack length or the pressure applied to the cracking cutters. Ordinarily, many cracking attempts had to be made before an adequate configuration was obtained, with corresponding regrinding (reflattening) and wastage of electrode length between each attempt In many cases, completed electrodes transferred to production departments have unsymmetrical and irregular crack configurations which do not work well in service
Consequently, a need exists for a different approach to producing a crack in an electrode tip that will more nearly and consistently resemble the ideal cruciform crack configuration.